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Re: Animating mixed units

From: Dr. Olaf Hoffmann <Dr.O.Hoffmann@gmx.de>
Date: Thu, 31 Mar 2011 11:43:48 +0100
To: www-svg@w3.org, jeremie.patonnier@gmail.com
Message-Id: <201103311243.49011.Dr.O.Hoffmann@gmx.de>
Hello,

I think, there is no specific problem in the SVG recommendations.
I think, I can simulate what is specified without problems, indeed I have
created last year 15 test cases, available in my test suite.

There are mainly two points:
1. It is obviously difficult to implement it right (this might require to 
convert all values with units to local coordinates before animating it,
concerning percentage, the conversion may change at any animation
step - therefore more difficult to implement than units with always the
same conversion factor).
2. The CSS2.1 draft introduces/suggests incompatible changes of the meaning
of px and absolute units, this might cause problem. Those changes are
not applicable for SVG, but some have implemented these changes
anyway for SVG.

Finally, my test result is, that typically all viewers fail.
Best results I get with Opera 9 (technical preview 2): 6/15
or with Batik/Squiggle: 5/15 or 
Opera 9.00/9.10: 5/15.
Compared to this for example Gecko 2.0 (Firefox 4) and WebKit
manage 0/15 and Opera 9.5-11 manages 2/15, the adobe plugin
1/15.

For authors the conclusion is currently: 
Don't even try it, the feature is broken.

In your case, calculate 100% in local coordinates manually and use this to
avoid nonsense.
In your example, r="0" may introduce additional complications for some
viewers, because r="0" has the specific rule not to display the circle at all.
Not sure, if all viewers manage this switch at the begin of the animation -
especially together with the unit complication.

Olaf



Olaf
Received on Thursday, 31 March 2011 10:44:23 GMT

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